Air Demand in a Dynamic Competitive Context with the Automobile (2019)

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

21 Introduction The past two decades have seen major changes in the role of shorter-distance air service, and this is correlated with a major increase in the role of the private automobile for shorter- distance trips. While metropolitan automobile tripmaking is either flat or down (depending on the specific years being examined), the portion of automobile travel devoted to the occasional long-distance trip is increasing, resulting in a rebound of total VMT rates from their dramatic declines after the recession of 2008. While the rate of air trips per person is only modestly higher over the past 20 years, the average length of the air trip has grown considerably: more air services are now offered for longer distances, with less air service for shorter distances. This chapter discusses changes in travel behavior and mode choice for shorter and longer distances over the past 20 years, examining in detail specific factors that have affected travel behavior and pinpointing the major corridors of market competition for the automobile and air travel modes. Market Trends for Air Travel, 1995 to 2017 Descriptions of air travel behavior are the most accurate and the most readily available to researchers because of the FAA’s interest in and oversight of air travel. The FAA publishes its update of the Terminal Area Forecast Summary annually, which “provides aviation data users with summary historical and forecast statistics on passenger demand and aviation activity at U.S. airports. The summary level forecasts are based on individual airport projections” (FAA 2016). Airport activity data for the period between 1995 and 2017 are summarized in Figure 2-1, taken from Terminal Area Forecast (TAF) 2017–2045. The enplanement data shown in Figure 2-1 illustrate the effects of two periods of economic upheaval. In the aviation sector (but not in the highway sector), there was a sharp decline between 2000 and 2002, which included the passenger market reaction to the attacks of September 11, 2001. Equally dramatic is the response of the market between 2003 and 2007, when the previous levels of enplanement were regained and increased upon substantially. The volumes at airports in the summer of 2007 were at an all-time high, with significant congestion occurring at busy airports like John F. Kennedy International Airport (JFK). From 2008 to 2009, during the depths of the Great Recession, the graph shows a sharp decline like the one in 2002. The industry rebounded with enplanement levels finally rising above those of 2007 by the end of 2015. In sum, there was about a 48% increase in total enplanements between 1995 and 2017. C H A P T E R 2 Trends and Changes in Automobile and Air Markets over Two Decades

22 Air Demand in a Dynamic Competitive Context with the Automobile In the study of modal choice between automobile and air services, it is particularly important to look at per capita patterns of transportation behavior—in this case, change in per capita rates of enplanement. A chart of enplanements per capita is presented as Figure 2-2, which shows a relatively linear pattern of increase in enplanements per capita between the base year of 1995 and 2000, followed by a more volatile period following the attacks of September 11, 2001, and declines around 2008. The per capita rate bounced back around 2014, resulting in a net increase of about 19% in the per capita rate between 1995 and 2017. Source: FAA, TAF Summaries 350 450 550 650 750 850 950 19 95 19 96 19 97 19 98 19 99 20 00 20 01 20 02 20 03 20 04 20 05 20 06 20 07 20 08 20 09 20 10 20 11 20 12 20 13 20 14 20 15 20 16 20 17 En pl an em en ts , i n m ill io ns Year Growth in Enplanements, 1995 to 2017 Figure 2-1. Airport enplanements, 1995–2017. Sources: TAF Summaries, U.S. Census 19 95 19 96 19 97 19 98 19 99 20 00 20 01 20 02 20 03 20 04 20 05 20 06 20 07 20 08 20 09 20 10 20 11 20 12 20 13 20 14 20 15 20 16 20 17 En pl an em en ts p er C ap ita 0.00 0.50 1.00 1.50 2.00 2.50 3.00 Year Growth in Enplanement per Capita, 1995 to 2017 Figure 2-2. Enplanements per capita, 1995–2017.

Trends and Changes in Automobile and Air Markets over Two Decades 23 Understanding the Services Provided by the Airlines Distribution of air travel services by distance between 2008 and 2011 was examined in Aviation Industry Performance: A Review of the Aviation Industry 2008–2011 (Office of Inspec- tor General, U.S. DOT 2012). A chart reproduced from that report (see Figure 2-3) illustrates the decrease in airline service as a function of the distance of the flight segment between 2008 and 2011. Figure 2-3 shows that this decrease in airline services occurred most strongly for flight segments shorter than 500 miles and almost entirely for flight segments shorter than 1,000 miles. This chart is presented to emphasize the fact that fewer flight segments are offered, affecting the combined frequency of flights from any given airport. In the years since 2011, the allocation of airline resources away from shorter-distance segments and to longer-distance segments has continued. In parallel with this trend, the role of automobiles in the shorter portion of the long-distance trip market has increased significantly over the past 20 years. The decline in air trip segments of under 500 miles has been well documented in the literature. In “What Caused the Short Haul Traffic Decline in the US?—the $34b Question,” a market analyst from Bombardier (a major supplier of shorter-distance aircraft) reviewed several possible explanations for the decline, noting, “As the total market has grown almost 30% since 2000, short-haul traffic under 500 miles has declined by the same amount, almost 30%” (Miller 2017). In Miller’s analysis, between 2000 and 2017, there was a 51% drop in O-D trips in the distance band between 100 and 200 miles, a 39% drop between 200 and 300 miles, and a 14% drop between 300 and 400 miles. Air tripmaking in O-D markets of longer than 400 miles showed a gradual increase with increasing distance, resulting in a total market increase of 30%. While the airports reporting such short-distance declines are well distributed around the country, notable exceptions are JetBlue at JFK and Long Beach, California, with Virgin American influencing an increase in traffic for trips of less than 500 miles at San Francisco International Airport (SFO) and increased utilization at Ronald Reagan Washington National Airport (DCA). Miller (2017) provides a valuable review of possible causes for the loss, including airline consolidation, raised prices on shorter segments, and the “hassle factor” of airport security following the attacks of September 11, 2001. Examining the reasons for a 40% decline in air Source: Office of Inspector General, U.S. DOT, 2012, Figure 26. Figure 2-3. Decrease in airline service by distance of flight segment, 2008–2012.

24 Air Demand in a Dynamic Competitive Context with the Automobile passengers between Dallas and Houston, Miller downplays the role of consolidation, accepts the logic of higher prices, and focuses squarely on the extra hour of “hassle” associated with security as tipping the door-to-door time comparison in favor of the automobile. Change in the Composition of Air Flight Segments, 1995 to 2016 In what the FAA TAF managers describe to as “the shift in the U.S. airline industry emphasis on market share to boosting returns on invested capital,” 1 airline managers have stopped asking the question about beating their competitors in weak markets and ask instead “which routes and services are profitable?” This means that the industry supplies fewer seats when there is less profit predicted. Holding the growth in the U.S. population aside, there is a change in seats offered per capita. Comparing the year 2017 with the year 2000 for trip distances less than 500 miles, seats offered per capita in 2017 were down by 34%; for distances between 500 and 1,500 miles, seats offered per capita in 2017 were essentially the same as two decades ago; and for longer trips, seats per capita in 2017 were up by 7%. Thus, the airlines have increased the portion of seats for longer trips and decreased the portion of seats for shorter trip segments, based on this comparison of T-100 trip segment descriptions from the FAA and the Bureau of Transportation Statistics (BTS). This, then, results in the average air trip segment getting longer on a rather consistent basis, as shown in Figure 2-4. The BTS computes the average trip length by dividing reported air passenger revenue miles by reported revenue enplanements,2 revealing the growth in air segment distance over time that is graphed in Figure 2-4. The examination of change in segment length is mirrored in the data about full trips taken. In 1995, 20% of O-D trips by air were less than 400 miles in length, according to the American Travel Survey (ATS); by 2011, only about 11% of air trips were less than 400 miles. 1 Federal Aviation Administration 2016, “Review of 2017,” p. 3. 2 BTS. Table 1-38: Average Length of Haul, Domestic Freight and Passenger Modes (Miles) https://www.bts.gov/content/ average-length-haul-domestic-freight-and-passenger-modes-miles. Source: BTS. Table 1-38: Average Length of Haul, Domestic Freight and Passenger Modes (Miles) https://www.bts.gov/content/average-length-haul-domestic-freight-and-passenger-modes-miles 720 740 760 780 800 820 840 860 880 900 920 M ile s Average Length of Air Segment, 1995 to 2015 Air carrier, domestic, scheduled 19 95 19 96 19 97 19 98 19 99 20 00 20 01 20 02 20 03 20 04 20 05 20 06 20 07 20 08 20 09 20 10 20 11 20 12 20 13 20 14 20 15 Figure 2-4. Increase in the length of the average air segment, 1995–2015.

Trends and Changes in Automobile and Air Markets over Two Decades 25 Changes in Air Travel, 1995 to 2016 Table 2-1 presents a quick summary of key changes in air travel between 1995 and 2016. The latest estimate for 2016 from the FAA TAF reports shows nearly 818,000,000 enplanements by commercial carriers at airports with FAA presence (FAA 2016). This represents an 18% growth (or a ratio of 1.18 to 1) in the per capita rate of enplanement since the base year. Phrased differently, the average American is boarding planes about 18% more than he/she was in 1995; about 1.4 segments are taken per full trip from airport of origin to airport of destination. Over the study period, the number of round trips per capita taken by air has increased from about .77 trips to .90 trips. Understanding Market Trends for the Automobile Historical Trends in VMT per Capita, 1995 to 2015 Overall, the trends in automobile use over the past few decades can be described as less volatile than trends in the aviation sector. The recent history of automobile travel includes a pattern of yearly increase in vehicle travel per person, plateauing around 2004 or 2005, as shown in Figure 2-5. At this point, VMT no longer consistently increases, with a pattern of 1995 2016 INCREASE 1995/2016 Enplanements* 565,235,549 817,964,902 45% Enplanement per capita 2.2 2.5 18% Trips at 1.4 segments per trip 403,739,678 584,260,644 45% Round trips 201,869,839 292,130,322 45% Round trips per capita 0.77 0.90 18% *FAA, TAF Summary 2017–2046, and historical data from TAF Summary 2024–2040 Table 2-1. Key changes in air tripmaking rates, 1995 vs. 2016. 4,000 5,000 6,000 7,000 8,000 9,000 10,000 11,000 VM T pe r Ca pi ta VMT per Capita, 1995 to 2017 Source: FHWA Travel Monitoring, Office of Highway Policy Information, accessed at https://www.fhwa.dot.gov/policyinformation/travel_monitoring/tvt.cfm; Year 2017 estimated from first quarter results by ACRP Project 03-40 research team. 19 95 19 96 19 97 19 98 19 99 20 00 20 01 20 02 20 03 20 04 20 05 20 06 20 07 20 08 20 09 20 10 20 11 20 12 20 13 20 14 20 15 20 16 20 17 Figure 2-5. VMT per capita (1995–2017).

26 Air Demand in a Dynamic Competitive Context with the Automobile decline to about 2013. Interestingly, the 2005 flattening occurred several years prior to the Great Recession, which also significantly affected aviation trip volumes. When the per capita rate for all (not just long distance) VMT for 2017 is compared with the base year of 1995, the rate of VMT generation per capita has increased by about 7% (or a factor of 1.07 to 1), although the rate is still lower than in its peak years. VMT as a Function of Economic Growth The timing of the flattening of the growth in VMT at the turn of the century is reflected in the examination of the relationship between VMT growth and gross domestic product (GDP) growth. Passenger Travel Facts and Figures includes a graph (see Figure 2-6) that charts GDP and VMT patterns between 1990 and 2014 (BTS 2016). The slope of the VMT line parallels the slope of the GDP between 1990 and 2005. From 2005, the slope of the GDP line continues upward until the Great Recession, in 2008, at which point it also declines. In short, the decoupling of VMT from the GDP pattern occurs somewhere around 2005 and continues downward until flattening at the end of the Great Recession. Figure 2-6 supports the argument that the altera- tion in the pattern of perpetual growth in automobile VMT cannot solely be attributed to larger economic patterns. VMT growth trailed the economic recovery until it reached prerecession levels by 2015. Thus, the national VMT levels have returned to historic highs, while VMT per capita rates have not. Air and Automobile Travel Together Growth and Volatility This research examined the relationship between highway travel and air travel and the growth in the two modes. The comparative volatility of the two modal trends can be seen in Figure 2-7, where the fluctuation in air enplanements is more pronounced than the fluctuation in automobile VMT. Figure 2-7 presents both automobile VMT and air enplanement growth lines in the form of an index of growth from 1991. The measure is absolute growth in VMT Source: BTS 2016. Figure 4-2. Figure 2-6. Comparison of GDP and VMT, 1990–2014.

Trends and Changes in Automobile and Air Markets over Two Decades 27 (not VMT per capita, as in Figure 2-5) in order to make a comparison with absolute growth in enplanements; thus, part of the growth in each travel mode is attributable to an increase in the U.S. population over this period. The volatility of air enplanements as compared with auto- mobile VMT is pronounced. Specifically, the sharp fall in enplanements between 2000 and 2002 is not mirrored in the VMT data, which show nearly linear growth between 1992 and 2005. In short, the 2001 decrease in enplanements was not mirrored in the automobile VMT data. Both air travel and automobile travel were affected by the Great Recession. However, air travel experienced a steeper decline than travel by automobile. (The base volume of auto- mobile VMT is much larger than air enplanements, making relative change more difficult to determine.) More recent data show a strong rebound in both air and automobile travel between 2013 and 2017. Mode Share by Distance (1995 vs. 2002) National long-distance data that systematically include travel by both automobile and air are provided in only two surveys: the ATS of 1995 and the National Household Travel Survey (NHTS) of 2001. The NHTS attempted to monitor both local and long-distance trips in one survey, with mixed results. An early review of the 1995 and 2001 data suggested that the role of the automobile for trips of less than 1,000 miles was significantly higher in the difficult period after the attacks of September 11, 2001.3 The research team compared air/automobile mode shares in the 1995 survey to those in the (smaller) 2001/2002 survey. Although the two surveys are not perfectly parallel, the results of the comparison showed that the relative role of the automobile in shorter long-distance trips had grown compared to the 1995 base year. The results of the long-distance travel survey conducted in 2017 under ACRP Project 03-40 tend to confirm the hypothesis of increased automobile reliance, but not to the degree observed in the volatile 2001 to 2002 data collection period. This finding is discussed in more detail later in this chapter. 0% 10% 20% 30% 40% 50% 60% Air Auto 19 95 19 96 19 97 19 92 19 93 19 94 19 98 19 99 20 00 20 01 20 02 20 03 20 04 20 05 20 06 20 07 20 08 20 09 20 10 20 11 20 12 20 13 20 14 20 15 Figure 2-7. Growth index from base year of 1992 for air enplanements and automobile VMT. 3 The analysis of change undertaken with 2001–2002 NHTS data is presented in ACRP Web-Only Document 38.

28 Air Demand in a Dynamic Competitive Context with the Automobile Long-Distance Travel Behavior in the Present and in 1995 Comparison with Earlier Mode Share Data The research team’s examination of the 2017 ACRP Project 03-40 survey results reveals a considerable level of stability in American long-distance travel patterns when compared with the 1995 base-year data. The preliminary results suggest that Americans’ long-distance trip- making by car has increased demonstrably in parallel to the growth of domestic enplanements. The analysis of the direct output of the 2017 survey data (i.e., not modified through simulation) shows an automobile mode share of 51% for trips exceeding 300 miles, which is somewhat higher than a directly comparable mode share of 46% from the 1995 ATS data. Automobile mode share is shown as a function of trip distance in Figure 2-8. Comparison with the Direct Results of the 2017 ACRP Project 03-40 Survey Important differences exist between the content of the 1995 ATS and the 2017 ACRP Project 03-40 survey. First, the surveys were undertaken for different purposes. The 1995 ATS sought to understand all long-distance travel in the United States. This ACRP Project 03-40 survey sought to understand travel from only four market survey areas—areas chosen to improve the understanding of the choice between smaller airports and larger airports in major markets. By contrast, the 1995 ATS was undertaken in all areas. To undertake this comparison, the 1995 ATS results were re-examined for trips beginning in the four U.S. Census divisions covered in the ACRP Project 03-40 survey: New England, South Atlantic, East North Central, and Mountain. Comparisons were made between 1995 curve for all divisions and the curves for just these four, resulting in the conclusion that there were no significant differences among them. Thus, to maximize the sample size, the curve based on the entire 1995 sample was used in the analysis. The research team restructured the 1995 ATS data to reflect only trips by air and automobile to facilitate comparison with the data collected in the 2017 survey, which only modeled those two modes. Thus, the “automobile mode share” in all cases represents the ratio of automobile trips to automobile-plus-air trips. A significant Source: Results from the 2017 ACRP Project 03-40 survey (not simulated data). 0% 10% 20% 30% 40% 50% 60% 70% 80% 300-700 700-1100 1100-1500 1500-1900 1900-2300 above 2300 A ut om ob ile M od e S ha re One-Way Trip Distance (miles) Automobile Mode Share by Trip Distance, 2017 Survey Compared with 1995 Full Sample 2017 1995 All Figure 2-8. Effect of distance on automobile mode share, 1995 vs. 2017 ACRP Project 03-40 survey results.

Trends and Changes in Automobile and Air Markets over Two Decades 29 increase in the mode share of automobiles between 1995 and 2017 is evident from Figure 2-8 for all but the shortest distance bands. Using ACRP Project 03-40 Simulated Data As described in Chapter 6, the research team developed a new analysis method to simulate (among other things) the mode choice of all long-distance trips in the lower 48 U.S. states. That national trip dataset was used in the creation of Figure 2-9 based on the simulation of millions of trips between 200 and 3,200 miles in length. Does an Increase in Car Use Make Sense? The overall pattern emerging from multiple data sources is that automobile travel has become more important for long-distance trips in general, with particular growth in trips less than 1,000 miles. The strong increase in automobile travel for these distances is generally consistent with the national trend, in which the national per capita VMT is about 7% higher in 2017 than it was in 1995. Thus, compared to the base year of 1995, overall driving is up modestly, using data that combines local and longer-distance trips together. Changes in Gas Prices The higher rate of automobile travel has occurred even though the price of gas has increased significantly. Gas prices at the pump were higher (adjusting for inflation) at the time of the 2017 ACRP Project 03-40 survey than at the time of the 1995 ATS survey. The research team estimates that the price of gas at the time of the survey was about 34% higher than it was in 1995 (adjusted for inflation). This summary of change in price was made after review of many sources, including U.S. Department of Energy, FWHA, and the American Automobile Associa- tion (AAA). This reinforces the well-documented observation that changes in gas prices do not predict changes in car use well. In sum, while the gas price rose by approximately one-third between 1995 and 2017, the travel rate rose by approximately 7%. 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 200-400 400-600 600-800 800-1000 1000-1200 1200-1400 1400-1600 1600-3200 A ut om ob ile a s % o f A ut om ob ile + A ir One-Way Trip Distance (miles) Automobile Mode Share by Distance, 1995 vs. 2011, with 2011 Simulation 1995 2011 Source: ACRP Project 03-40 Scenario Testing Model Figure 2-9. Change in automobile share, 1995 vs. 2011 simulation.

30 Air Demand in a Dynamic Competitive Context with the Automobile Changes in Air Fares The relationship between frequency of air travel and the price of air travel is more intuitive. Reviewing several sources4 of data produces multiple estimates of how much the cost of air travel has decreased on a per mile basis, but the latest updates from the airline industry suggest that compared to the estimates for the 1995 base year, the cost has dropped by more than half (Thompson 2013). Figure 2-10 combines the results of searches for cost data for gas and airline tickets. A Major Finding: An Overall Change in Composition of VMT? Automobile Mode Share for Long-Distance Trips The results of the analysis suggest that the role of the automobile in long-distance trips has increased significantly over the past two decades. The national simulation model created for ACRP Project 03-40 supports the ability to undertake more precise analyses of national data. Table 2-2 shows the 2011 automobile share of automobile-plus-air trips compared with 1995 values for all distance bands of more than 200 miles. Several different data sources of present automobile use show that between 1995 and the present there is a consistent pattern of increase in automobile share for most distance bands. The simulation modeling for this research also supports the finding of a major increase in the role of the automobile in long-distance trips between 1995 and the present. The parallel trip- making patterns for air travel are also clear, based on the empirically observed decrease in 0 0.1 0.2 0.3 0.4 0.5 0.6 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 C o st p er m ile ( d o lla rs ) Air (ticket price only) Auto (gas price only) Figure 2-10. Cost of airline tickets and gas over time. 4 Several sources were reviewed. Those in Figure 2-10 came from http://www.planetickets.com/airfare.html. Gas prices over time in Figure 2-10 came from “Gasoline price history,” a web page from the website Random Useless Info at www.randomuseless.info/ gasprice/gasprice.html.

Trends and Changes in Automobile and Air Markets over Two Decades 31 both flights (seats) and passenger enplanements for shorter air trips. Thus, the “Share of all trips longer than 200 miles” row in Table 2-2 shows that in 1995 the air system alone carried about 40% of the market for trips longer than 200 miles and in 2011 carried about 23% of that market. This chapter has noted that both air travel and VMT volumes change on a year-by-year basis, so the 23% figure should be seen as indicative of a value within a reasonable range, plus or minus. Further, the reader is reminded again that the automobile volumes for 1995 came from an actual nationwide survey, while the automobile volumes used in the calibration process for the research team’s model came from modeling and estimate procedures used by FHWA. None- theless, the overall pattern of a decrease in the mode share of the air system for shorter trips and an increase in the mode share of the automobile for such trips is supported by a wide variety of analyses undertaken in ACRP Project 03-40. Long-Distance Automobile Travel as a Portion of Total Automobile Travel Under most definitions, long-distance trips are trips of more than 100 miles. Looking this time at the total long-distance market (including trips between 100 and 200 miles), the research team estimates that the automobile mode share was 77% in 1995 and rose to 85% in the 2011 calibration year. Seen as automobile miles per capita, this translates to approximately 2,700 VMT per capita of long-distance travel, a significant component of the 9,400 total VMT per capita reported in that year. In this 2011 travel pattern, automobile trips of more than 100 miles for whatever purpose account for 29% of vehicle miles taken in the year. This percentage (29%) represents a larger role for the long-distance trip than is often used when calculating the composition of component elements of VMT and should be a subject of further research. By way of comparison, in 1995, using the same set of assumptions as used above trips of more 100 miles represented about 17% of total VMT per capita. AUTOMOBILE SHARE OF AUTOMOBILE + AIR TRIPS Distance Band (miles) 1995 2011 200–400 86% 95% 400–600 68% 83% 600–800 47% 72% 800–1000 37% 59% 1,000–1,200 30% 45% 1,200–1,400 22% 36% 1,400–1,600 19% 28% 1,600–3,200 9% 16% Total above 200 miles 60% 77% Source: 1995 ATS; FHWA National Model, RSG from national trip model created in foundational research study (see RSG 2015b) Table 2-2. Automobile mode share of long-distance trips by distance, 1995 vs. 2011.

32 Air Demand in a Dynamic Competitive Context with the Automobile Where the Competitive Markets Are Located Corridors Less than 800 Miles in Distance There are only a finite number of corridors (or city pairs) were the automobile and air modes actually compete. Even within the lower 48 states, the propensity of a given corridor (or city pair) to offer travel options that are truly competitive varies widely. A trip from Seattle to Key West by car cannot be competitive with air service; a 400-mile trip by airplane from Hartford, Connecticut, to Buffalo, New York, is presently almost illogical. This examination is focused on the top intercity markets where air travel and the automobile realistically compete. The research team’s work program was designed to allow the examination of 1-day automobile trips separately from trips that would require an overnight stay. The research team defined the top “1-day” markets, using trip tables originally developed to explore the possible role of buses in corridors. That study reviewed all candidate city pairs with more than 100 miles between them and assumed that corridors with no reported bus service should not be included in the top 200 markets (FHWA 2015). For ACRP Project 03-40, that list was further narrowed by including only those city pairs with an air mode share of more than 2%. Figure 2-11 shows all the market corridors between 100 and 800 miles that meet this definition. In only 69 city pairs is air travel a reasonable competitor to the automobile. In Figure 2-11, these cities are rank ordered by total travel by all modes. (The relationship between trip distance and air mode share for the city pairs included in Figure 2-11 can be depicted in graph format, as shown in Figure 2-12.) In most of the corridors, the two modes together account for less than 2 million annual trips. As shown in Figure 2-11, only 19 city pairs generated more than 2 million long-distance trips per corridor in the base year of 2008. Another 33 city pairs are included on the list with travel volumes between 1 million and 2 million annual trips. An additional 17 city-pair markets are shown with volumes of 1 million annual trips and less. Relatively small variations in definitions could change the number of city pairs listed in Figure 2-11. The Great Circle Route distance from New York’s City Hall to Philadelphia’s City Hall is 81 miles. Actual routing distance between the two cities (derived from Google Maps) by I-95 is about 98 miles—making it a potential candidate for consideration in a study of distances around 100 miles. New York City/Philadelphia would emerge as the single largest intercity pair corridor in the United States with a slightly different set of definitions. If it had been included, the New York City/Philadelphia volume would be approximately 19 million interregional trips, with an air share of 3%. At a 90-mile distance, Los Angeles/San Diego would show approximately 21 million interregional trips, but this city pair has insignificant O-D air share reported and thus doesn’t meet the air mode share criterion for the list. Examples of the Scale of Tripmaking for Trips Longer than 800 Miles The longest distances included in this section include trips that might be made by auto- mobile in 1 (very long) day, such as Chicago/New York and Chicago/Dallas, which are more than 700 miles and have air mode shares around 90%. Not many drivers travel more than 800 miles in a single daily driving segment. However, a sense of scale for the longer trips can also be gained by examining a small set of long-distance air volumes that are empirically reported. Project modeling has been under- taken by the research team for a study of airport choice in multi-airport settings that—as an

Source: ACRP Project 03-40 research team. Based on data from FHWA bus study (FHWA 2015). Annual Trips by All Modes (millions) Figure 2-11. One-day drive corridors (100–800 miles, air mode share greater than 2%) ranked by total traffic volume.

34 Air Demand in a Dynamic Competitive Context with the Automobile example—includes the examination of air volumes from all of the airports in the Los Angeles area to all of the airports in the New York area5. Examples of air passenger flows between metro regions are the following: • New York City/Los Angeles—4.4 million air passengers; • New York City/Bay Area—3.1 million air passengers; • Los Angeles/Chicago—2.7 million air passengers; and • Chicago to all the airports competing with Boston/Logan—2.3 million air passengers. Current data suggest that each of these air volumes is associated with an automobile volume that results in automobile mode shares between 3% and 5%. 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 100 200 300 400 500 600 700 800 A ir M od e S ha re Distance (Miles in Great Circle Distance) Source: Data from Figure 2-11. Mode share data available in ACRP Web-Only Document 38. Figure 2-12. Air mode share by distance for the 1-day-drive city pairs. 5 This analysis of choice between dominant airports and smaller airports is included in ACRP Web-Only Document 38.